1. Field of the Invention
This invention relates to a process and apparatus (system) which can be used as a new method for the preheating and coating of pipe weld joints with a coating material which should be heated to a predetermined temperature for its proper adhesion to the pipe. In the case of a powdered epoxy material, for example, this desired temperature would be the fusion and/or curing temperature. In case of liquid coating materials, this temperature could be the curing temperature or, sometimes, simply the temperature at which the material will flow readily over the pipe surface. More particularly, this invention involves an arcuate or circumferential, rotatable yoke which is adapted to be mounted on a pipe or pipeline in order to heat the underlying area of a weld joint so, that, when a coating material is applied immediately thereafter, the coating material will reach the proper application temperature. The present system differs from the circular coil now popularly used for this task in that the heater elements are not themselves wrapped around the pipe in the form of a coil or coils, but arranged as a plurality of separate, longitudinally-oriented induction heaters spaced around the pipe above the surface thereof parallel to the longitudinal axis of the pipe; since the powder applicator is also mounted on the same supporting ring for the heaters, the system provides a method whereby the weld joint can be heated and coated (even simultaneously, if desired) without the need for moving the supporting ring longitudinally along the pipeline.
2. Prior Art
A preliminary search was conducted on the present invention and the following patents represent the results of the search:
______________________________________ Patentee U.S. Pat. No. Issue Date ______________________________________ Hughes 4,388,510 June 14, 1983 Fugill 2,180,513 November 21, 1939 Wright 2,596,636 May 13, 1952 Williamson 2,715,171 August 9, 1955 Suelen et al 2,743,345 April 24, 1956 Wokas 3,188,440 June 8, 1965 Reinke 3,359,398 December 19, 1967 Preyer 3,354,514 January 12, 1971 ______________________________________
Hughes U.S. Pat. No. 4,388,510 (owned by the assignee of the present invention) merely shows one type of circular induction coil for heating the area of a weld joint on a pipeline.
Fugill et al U.S. Pat. No. 2,180,513 shows another form of a circular induction coil for relieving stesses in welds on a pipe.
Wright U.S. Pat. No. 2,596,636 shows a dielectric heating apparatus which can be manipulated in the manner of a flat iron and which is supported on roller-type electrodes 9. Whereas this reference shows a primary winding 5 and a secondary winding 8 which receive high frequency energy (much higher than that of the present invention), the heating takes place in the capacitive portion of the circuit.
Williamson U.S. Pat. No. 2,715,171 is considered to be pertinent in a general sense, but the pipe "A" to be heated has to fit between the side conductor 12 and be in a position adjoining the central conductor 16. The conductor 16, however, is hollow so that cooling water can be circulated therethrough. Also, the conductor 16 is covered with a stack of thin flat laminations 17 which are similar to the ferrous plates employed in the present invention.
Seulen et al U.S. Pat. No. 2,743,345 shows a wheeled heater supported on rollers 4 around a concave recess 3 in which a cylindrical workpiece, such as a pipe, may be disposed. The heating circuit includes a heating conductor loop 6 including a conductor 9 (see FIG. 4), and two lead sections 10. These current carrying members are copper tubes through which cooling water is allowed to flow. It appears that item 11 is a plurality of yoke laminations as referred to in column 3, lines 66 through 68. This reference apparently relates to low frequency induction heating.
Wokas U.S. Pat. No. 3,188,440 is described as a high frequency inductor assembly. In column 2, lines 48 through 50 it is stated that the inductor can be readily applied to an inductor assembly of the type shown in Seulen et al U.S. Pat. No. 2,743,345 which was discussed above. Items 16 and 17 are guides. The entire inductor assembly 10, as shown in FIG. 2, is supported from a housing 57 by means of bars 56. The housing 57 is supported on a carriage 58 having wheels 59 which engage a track 60. Wokas is obviously dealing with an apparatus which is totally different from the present invention as far as structure and operational capability are concerned. Wokas, however, does disclose hollow copper pipes through which cooling liquid is allowed to flow and also U-shaped laminations on the side conductors 23 and 24.
Reinke et al U.S. Pat. No. 3,359,398 shows liquid cooled hollow conductors 1 arranged to form a closed conductor loop extending across the cylindrical surface of a workpiece 5 and carrying laminated iron yokes 6.
Preyer U.S. Pat. No. 3,554,514 shows a device for inductively heating and hardening of the crank pin of a crankshaft.